US5262556A - Process for the reaction of halogenated aromatics with electrophiles - Google Patents

Process for the reaction of halogenated aromatics with electrophiles Download PDF

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US5262556A
US5262556A US07/879,238 US87923892A US5262556A US 5262556 A US5262556 A US 5262556A US 87923892 A US87923892 A US 87923892A US 5262556 A US5262556 A US 5262556A
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electrophile
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Bernard Riefling
Jurgen Seubert
Volker Reiffenrath
Reinhard Hittich
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Merck Patent GmbH
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    • C07C25/18—Polycyclic aromatic halogenated hydrocarbons
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    • C07—ORGANIC CHEMISTRY
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    • C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
    • C07C41/01—Preparation of ethers
    • C07C41/18—Preparation of ethers by reactions not forming ether-oxygen bonds
    • C07C41/30—Preparation of ethers by reactions not forming ether-oxygen bonds by increasing the number of carbon atoms, e.g. by oligomerisation
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    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
    • C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
    • C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D213/61—Halogen atoms or nitro radicals
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    • C07F5/00—Compounds containing elements of Groups 3 or 13 of the Periodic Table
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    • C07F7/00—Compounds containing elements of Groups 4 or 14 of the Periodic Table
    • C07F7/02—Silicon compounds
    • C07F7/08—Compounds having one or more C—Si linkages
    • C07F7/0803—Compounds with Si-C or Si-Si linkages
    • C07F7/081—Compounds with Si-C or Si-Si linkages comprising at least one atom selected from the elements N, O, halogen, S, Se or Te
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    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
    • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
    • C09K19/14—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings linked by a carbon chain
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    • C09K19/06—Non-steroidal liquid crystal compounds
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    • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
    • C09K19/3001—Cyclohexane rings
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    • C09K19/0403—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit the structure containing one or more specific, optionally substituted ring or ring systems
    • C09K2019/0407—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit the structure containing one or more specific, optionally substituted ring or ring systems containing a carbocyclic ring, e.g. dicyano-benzene, chlorofluoro-benzene or cyclohexanone

Definitions

  • the invention relates to a process for the reaction of halogenated aromatics with electrophiles at the ortho position relative to the halogen atom, in which a strong base is added to a mixture of the halogenated aromatic and the electrophile.
  • Halogenated aromatics substituted in the ortho position relative to the halogen atom are important intermediates in industrial organic chemistry.
  • Suitably substituted derivatives are in particular valuable intermediates for the synthesis of high-value end products or are themselves such end products for the electronics industry, for example liquid crystals, for crop protection, for example pesticides, or for the preparation of pharmaceutically highly active substances, for example dopamine receptor blockers, antiemetics or antipsychotics.
  • the corresponding phenol is formed from the boronate by oxidation with hydrogen peroxide.
  • WO 89/2425 describes the preparation of liquid-crystalline 2,3- and 2',3'-difluoro-p-terphenylene, starting from 1,2-difluorobenzene.
  • WO 89/8629 describes the preparation of further different liquid-crystalline compounds containing a 2,3-difluoro-1,4-phenylene group.
  • the 1,2-difluorobenzene or 1-substituted 2,3-difluorobenzene is deprotonated with a strong base, usually n-butyllithium, and the 2,3-difluorophenyllithium compound obtained is reacted with an electrophile.
  • o-fluorophenyl derivatives can be prepared from the corresponding o-fluorobromobenzenes by reaction with magnesium to give o-fluorophenylmagnesium bromide, followed by derivatization (for example EP 0,238,272). In this case too, it is imperative to work at low temperatures.
  • an object of the present invention is to find a preparation process for halogenated aromatics substituted in the ortho-position, particularly o-fluoro- or o-chlorophenyl derivatives which does not have the above-described disadvantages of the previous processes and can be carried out without risk on a large industrial scale.
  • the invention relates to a process for the reaction of fluorinated or chlorinated aromatics with electrophiles at the ortho position relative to the fluorine atom, characterized in that a strong base is added to a mixture of the fluorinated or chlorinated aromatic and the electrophile, in particular to a process for the preparation of fluorinated or chlorinated aromatics of the formula I, ##STR3## in which L 1 and L 2 are each, independently of one another, F or Cl
  • R 1 is H, F, alkyl, alkenyl, alkoxy each having up to 18 carbon atoms or a mesogenic group,
  • W, X and Y are each, independently of one another, N, CH or CL 2
  • R 2 is alkyl having 1 to 15 carbon atoms or a mesogenic radical corresponding to the group R 1 ,
  • BX 2 is a trioxatriborinane radical of the formula ##STR5## in which Z is ##STR6## or a group of the formula --B(OR 3 ) (OR 4 ), R 3 and R 4 are H, alkyl, alkenyl or cycloalkyl each having up to 10 carbon atoms, or taken together are an alkylenediyl group of the formula --(CH 2 ) n -- or --CH 2 CHR 8 --CH 2 --, in which n is 2, 3 or 4 and R 8 is alkyl, alkoxy or alkenyl having up to 18 carbon atoms, or a mesogenic radical corresponding to the formula II, and
  • SI is a trihydrocarbylsilyl group of the formula --Si(R 5 ) 3 , in which each R 5 is, independently of the others, an aliphatic radical having 1-6 C atoms, cycloaliphatic radical having 4-10 C atoms, araliphatic radical having 7-10 C atoms or aromatic radical having 6 to 10 C atoms.
  • the invention relates in particular to those processes in which R 1 is a mesogenic group of the formula II, in which
  • R 0 is an alkyl or alkenyl radical having up to 15 carbon atoms which is unsubstituted or monosubstituted by CN, halogen or CF 3 , it being possible for one or more CH 2 groups in these radicals to be each replaced, independently of one another, by --S--, --O--, --CO--, --CO--O--, --O--CO-- or --O--CO--O-- such that S and/or O atoms are not linked directly to one another.
  • Z 1 and Z 2 are each, independently of one another, --CH 2 CH 2 --, --C.tbd.C--, --CH 2 O--, --CO--O--, --O--CO--, --CH ⁇ N--, --N ⁇ CH--, --CH 2 S--, --SCH 2 --, a single bond or an alkylene group having 3 to 6 carbon atoms. in which one CH 2 group can also be replaced by --O--, --CO--O--, --O--CO--, --CHhalogen- or --CHCN--, and
  • a 1 and A 2 are each, independently of one another,
  • (c) a radical from the group comprising 1,3-cyclobutylene, 1,3-bicyclo[1.1.1]pentylene, 1,4-cyclohexenylene, 1, 4-bicyclo[2.2.2]-octylene, piperidine-1,4-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl and 1,2,3,4-tetrahydronaphthalene-2,6-diyl,
  • radicals (a) and (b) it being possible for the radicals (a) and (b) to be substituted by CN or halogen, and
  • n 0, 1 or 2.
  • R 5 is aliphatic, preferred is 1-4 C atoms, in particular methyl, ethyl or tert-butyl; cycloaliphatic, particularly preferred is 5-7 C atoms; araliphatic, particularly preferred is benzyl; aromatic, particularly preferred is phenyl or tolyl.
  • the invention relates to the use of the o-fluoro- or chloroarylboronic acids or esters thereof of the formula IB, prepared by the process according to the invention, for the preparation of the corresponding o-fluoro- or chlorophenols, in particular of 2,3-dichlorophenol, 2,3-dichlorohydroquinone, 2,3-difluorophenol and 2,3-difluorohydroquinone, by oxidative hydrolysis, to their use as coupling components in transition-metal-catalyzed cross-coupling with halogen or perfluoroalkyl sulfone compounds, and for the preparation of the corresponding o-fluoro- or chlorohaloaromatics by halogenation.
  • R 6 is F, alkyl having 1-15 C atoms, C 1 -C 15 -alkyl ##STR10## n is 1 or 2, ##STR11## in which L 1 , L 2 , R 3 and R 4 are as defined, and R 7 is H, F, alkoxy each having up to 18 carbon atoms or a mesogenic group corresponding to the formula II,
  • R 6 is an alkyl
  • preferred is 1-10 C atoms, in particular 2-9 C atoms.
  • o-fluoro- and o-chloroaryl derivatives prepared by the process according to the invention comprise mono-, di-, tri-, tetra- and penta-fluoro- and -chlorophenyl derivatives.
  • 2-fluoro- and 2-chloropyridin-3-yl derivatives can also be prepared by the process according to the invention. Whether or not further substituents are present on the aromatic ring apart from the fluoro and chloro substituents, is not critical for carrying out the process according to the invention. Examples of further substituents are alkyl, alkenyl or alkoxy groups, bromine or mesogenic groups.
  • the fluorinated and chlorinated aromatic rings can also be constituents of fused ring systems, such as, for example, of naphthalenes, di- and tetrahydronaphthalenes or of 2,3,4,5-tetrahydro-1H-3-benzazepine derivatives.
  • Phe is a 1,4-phenylene group, in which one or two CH groups can also be replaced by N, it being possible for a 1,4-phenylene group also to be substituted by one or two halogen atoms
  • ArL is a fluorinated or chlorinated 1,4-phenylene group of the formula ##STR12## in which L 1 is F or Cl, and L 3 , L 4 and L 5 are each, independently of one another, H, Cl or F.
  • Cy is a trans-1,4-cyclohexylene radical, in which one or more non-adjacent CH, groups can also be replaced by --O--.
  • E is a group introduced by the reaction according to the invention.
  • BX 2 is a trioxatriborinane radical of the formula ##STR13## in which Z is the o-fluoro- or o-chlorophenyl group defined in each case,
  • R 3 and R 4 are as defined, R 3 and R 4 being preferably identical and having the meaning of hydrogen, methyl or isopropyl.
  • Preferred alkylation and hydroxyalkalation reagents are the compounds of the formula IIIa to IIIf: ##STR15## in which R 2 is alkyl having 1 to 15 carbon atoms or a mesogenic group corresponding to the formula II, ##STR16## is ##STR17## m is 1 or 2 and X 1 is Cl, Br, iodine or a perfluoroalkylsulfonyloxy group wherein the alkyl group has 1-10 C atoms, in particular 1-4 C atoms.
  • Silylating reagents are the compounds of the formula IIIg, SI-L, in which SI is as defined and L is a leaving group, in particular compounds of the formulae IIIga to IIIgh: ##STR18##
  • B(OR 3 ) (OR 4 ) (Oalkyl), in particularly B(Oalkyl) 3 are suitable.
  • the O alkyl group has 1-10 C atoms preferably 1-4 C atoms, and is most preferably a methoxy group.
  • the compounds of the formula I prepared by the process according to the invention comprise those of the formula Ia to Ig ##STR19##
  • L 1 and L 2 are preferably F
  • R 1 is preferably H, alkyl or alkoxy each having 1 to 12 carbon atoms or a mesogenic radical, particular preference in the process according to the invention being given to the compounds of the formula Ib, in which R 1 is H or alkoxy having 1 to 12, particular 2 to 4, carbon atoms.
  • R 1 is H or alkoxy having 1 to 12, particular 2 to 4, carbon atoms.
  • the compounds of the formulae I1, I2, I3, I4 and I7 are particularly preferred, in particular those in which ArL is a radical of the formula ##STR21## and L 3 , L 4 , L 5 are H or F.
  • R 1 is an alkyl group preferably having 1 to 10 carbon atoms, or an alkoxy or an alkenyl group each preferably having 1 to 10 carbon atoms.
  • L 1 is preferably F
  • L 2 is preferably F and, in the case where
  • L 1 is Cl, preferably Cl.
  • Particularly preferred alkyl groups are hexyl, pentyl, butyl, i-butyl, propyl, i-propyl, methyl and ethyl, in particular methyl; particularly preferred alkoxy groups are hexoxy, pentoxy, i-butoxy, propoxy, i-propoxy, methoxy and ethoxy, in particular methoxy; particularly preferred alkenyl groups are hexenyl, pentenyl, butenyl and allyl.
  • the alkyl radicals in which a CH 2 group (alkoxy or oxaalkyl) can also be replaced by an O atom can be straight-chain or branched.
  • a 1 and A 2 are preferably Cyc or Phe.
  • Phe is preferably a 1,4-phenylene (Ph), a 1,4-phenylene group mono- or disubstituted by F or CN (PheX), a pyrimidin-2,5-diyl (Pyr), a pyridin-2,5-diyl (Pyn), a pyrazin-3,6-diyl or a pyridazin-2,5-diyl group, is particular preferably Ph, PheX, Pyr or Pyn.
  • the compounds prepared by the process according to the invention preferably contain not more than one 1,4-phenylene group, in which one or two CH groups are replaced by N.
  • Cyc is preferably a 1,4-cyclohexylene group.
  • one of the groups A 1 and A 2 is a 1,4-cyclohexylene group substituted in the 1 or 4 position by CN and the nitrile group is in the axial position, i.e., the group A 1 or A 2 has the following configuration: ##STR24##
  • --Phe-Phe-- is preferably --Ph-Ph--, Pyr-Phe or Ph-Pyn.
  • Particular preference is given to the groups ##STR25## and furthermore to 4,4'-biphenylyl which is unsubstituted or mono- or polysubstituted by fluorine.
  • the groups Z 1 and Z 2 are each, independently of one another, preferably a single bond, secondly preferably --C.tbd.C-- or --CH 2 CH 2 -- groups. In particular, preference is given to compounds of the formula I in which the group Z 1 is --CH 2 CH 2 --.
  • Branched groups of this type usually contain not more than two chain branchings.
  • R 1 is preferably a straight-chain group or a branched group having not more than one chain branching.
  • the radical R 1 can also be an optically active organic radical containing an asymmetric carbon atom.
  • the asymmetric carbon atom is then linked to two differently substituted carbon atoms, an H atom and a substituent selected from the group comprising fluorine, alkyl or alkoxy each having 1 to 5 carbon atoms and CN.
  • the optically active organic radical R 1 preferably has the formula ##STR26## in which X' is --O--, --S-- or a single bond,
  • Q' is alkylene having 1 to 5 carbon atoms, in which one CH 2 group not linked to X' can also be replaced by --O--, or a single bond,
  • Y' is CN, F, CF 3 , methyl or methoxy
  • R 7 ' is an alkyl group different from Y' and having 1 to 15 carbon atoms, in which one or two non-adjacent CH 2 groups can also be replaced by --S--, --O--.
  • X' is preferably a single bond.
  • Q' is preferably --CH 2 --, --CH 2 CH 2 --, --CH 2 CH 2 CH 2 -- or a single bond, in particular preferably a single bond.
  • Y' is preferably CH 3 , --CN or F, in particular preferably CN or F.
  • R 7' is preferably straight-chain or branched alkyl or alkoxy having 1 to 10, in particular 1 to 7, carbon atoms.
  • the new compounds of the formula IA are also provided by the present invention. Of these, the compounds of the formulae IAa, IAb, IAd and IAg are particularly preferred.
  • the process according to the invention is suitable for preparing new difluoro-1,4-phenylenediboronic acids or anhydrides thereof the formula IB3, ##STR29## in which L 1 is F and one of the radicals L 2 is F or L 1 is Cl and one of the radicals L 2 is Cl.
  • L 1 is F and one of the radicals L 2 is F or L 1 is Cl and one of the radicals L 2 is Cl.
  • MG 1 , MG 2 are mesogenic groups corresponding to the radical of the formula II
  • X 1 , Y 1 is a halogen or perfluoroalkylsulfonyloxy, preferably iodine, bromine or triluromethylsulfonyloxy.
  • the new difluoro- and -chlorophenylboronic acids of the formulae IB1 and IB2 are furthermore suitable for preparing new liquid-crystalline difluoro- or -chlorophenyldioxaborinanes of the formulae IB1a and IB2a ##STR31## in which R' is as defined, and R 8 is alkyl, alkenyl or alkoxy having up to 18 carbon atoms or a mesogenic group corresponding to the formula II.
  • the new difluoro- and -chlorophenyldioxaborinanes of the formula IB1a and IB2a are also provided by the invention.
  • An aromatic is an organic compound containing one or more unsaturated rings and having 5-10 carbon atoms, the rings may be fused or covalently bonded. It also includes unsaturated heterocyclic ring structures with at least one N, S and/or O ring/atom.
  • the halogenated aromatic is a compound with a chlorinated or fluorinated benzene, pyridine, pyrimidine or pyridazine group in which there is a hydrogen atom in the o-position relative to the halogen atom.
  • the reaction procedure of the process according to the invention is simple and comprises reacting the starting materials at temperatures of -100° to 100° C., preferably -40° to 40° C., in particular 0° to 35° C., and at elevated or reduced pressure, preferably at atmospheric pressure.
  • a significant advantage of the process according to the invention compared with that known from the prior, art is the fact that it is not necessary to work at low temperatures (-100° to -65° C.), in order to prevent explosive decomposition of the o-fluoro- or o-chlorophenyllithium at elevated temperatures, since this compound is only formed in situ and is always trapped by the alkylating or hydroxyalkylating agent present.
  • the fluorinated aromatic is initially introduced in a mixture with the electrophile in an inert solvent, and the strong base is added.
  • the reaction can be carried out in the absence or, advantageously, in the presence of an inert solvent, suitable solvents being the conventional solvents for reactions with strong bases, for example ethers, such as diethyl ether, tetrahydrofuran or methyl tert.-butyl ether, hydrocarbons, such as pentane, hexane, heptane, benzene, toluene, xylene or cyclohexane or mixtures of the solvents mentioned.
  • cosolvents such as, for example, hexamethylphosphoric triamide (HMPT), tetramethylethylenediamine (TMEDA), dimethylpropyleneurea (DMPU) or crown ethers, such as 18-crown-6, to these solvents.
  • HMPT hexamethylphosphoric triamide
  • TEDA tetramethylethylenediamine
  • DMPU dimethylpropyleneurea
  • crown ethers such as 18-crown-6
  • the amount of solvent is not critical, it being in general possible to use 100 to 1000 g of solvent per mole of fluorinated aromatic compound.
  • An electrophile is an electron pair acceptor which seeks the electron rich center of an organic compound.
  • Suitable electrophiles include alkylating or hydroxylating agents, silylating agents and trialkyl borates.
  • Suitable electrophiles are the compounds mentioned of the formulae IIIa to IIIf, preferably n-alkyl halides having 1 to 16 carbon atoms, in particular n-alkyl bromides and iodides, such as, for example, methyl bromide, ethyl bromide, propyl bromide, butyl bromide, pentyl bromide, hexyl bromide, heptyl bromide, octyl bromide or nonyl bromide or methyl iodide, ethyl iodide, propyl iodide, butyl iodide, pentyl iodide, hexyl iodide, heptyl iodide, octyl iodide or nonyl iodide, n-alkanals having 2 to 16 carbon atoms, in particular acetaldehyde, propionalde
  • Suitable silylating agents are the compounds of the formulae IIIg, preferably trialkylsilyl halides in which the alkyl groups are straight-chain or branched and have 1 to 8 carbon atoms, in particular the compounds of the formulae IIIga to IIIgf.
  • Suitable trialkyl borates are usually compounds of the formula B(OR 3 ) 2 (OR 1 ), preferably B(OR 3 ) 3 , in which R 3 is methyl, ethyl, propyl, butyl or isopropyl, in particular methyl or isopropyl.
  • strong base The type of the strong base to be used depends on the fluorinated aromatics used. Usually, the strong bases customary in organic chemistry are used (for example House: Modern Synthetic Reactions 2nd Ed., Benjamin 1972, p. 547). Particularly suitable strong bases are alkali metals, such as lithium, sodium or potassium, alkali metal hydrides, such as lithium hydride, sodium hydride or potassium hydride, alkaline earth metal hydrides, such as calcium hydride, organometallic compounds, such as n-butyllithium, sec.-butyllithium, tert.-butyllithium, methyllithium, ethyllithium or phenyllithium, in particular n-butyllithium, strong amide bases, such as sodium amide, potassium amide, lithium diisopropylamide, lithium cyclohexylisopropylamide, lithium dicyclohexylamide, 2,2,6,6-tetramethylpiperidin-1-y
  • a further advantage of the process according to the invention is that it is at any time safe to interrupt and resume later, since only unreactive compounds, such as the fluorinated aromatic, the alkylating or hydroxyalkylating agent, metal alcoholate and the o-fluoro- or chloroaryl derivative, are present during the dropwise addition of the base.
  • unreactive compounds such as the fluorinated aromatic, the alkylating or hydroxyalkylating agent, metal alcoholate and the o-fluoro- or chloroaryl derivative
  • the fluoro- or chloroaromatic is initially introduced together with about 10-80%, in particular 15-25%, of the electrophile to be used in an inert solvent, preferably tetrahydrofuran, and the base, preferably lithium diisopropylamide, is added simultaneously in an inert solvent under an inert gas atmosphere together with the remaining amount of the electrophile (20-90%, preferably 75 to 85%).
  • an inert solvent preferably tetrahydrofuran
  • the base preferably lithium diisopropylamide
  • 0.8 to 2.2 mol, preferably 1.2 to 1.8 mol of base and 0.8 to 1.5 mol, preferably 1.0 to 1.3 mol of electrophile are required for 1 mole of the fluoroaromatic to be deprotonated.
  • reaction mixture and isolation of the products is carried out in the usual manner, for example by pouring the reaction mixture into water and/or onto ice or into dilute acid and separating off the aqueous phase, followed by recovering the o-fluoro- or chloroarylboronic acid derivative by distillation or crystallization.
  • the process according to the invention makes it possible to prepare the o-fluoro- or chloroaryl derivatives, which are valuable intermediates, for example for liquid crystals, auxiliaries, crop protection agents and pharmaceuticals, in a simple manner, without risk, on a larger scale and in higher yields compared with the prior art.
  • arylsilanes according to the invention of the formula IA can be used to prepare o-fluorinated halogenzene derivatives according to Scheme 2: ##STR34##
  • the 1 H nuclear magnetic resonance spectra were recorded using a 200 MHz spectrometer from Bruker.
  • a solution of 0.02 mol of lithium diisopropylamide in THF/hexane (prepared analogously to Example 1) is added dropwise at 25° C. to a mixture of 0.2 mol of 2,6-difluoropyridine, 0.02 mol of N,N-dimethylethyleneurea, 0.02 mol of 2-(4'-propylbicyclohexyl-4-yl)-1-iodoethane and 25 ml of THF. Stirring for 1.5 hours and workup as described in Example 1 give the pure product.
  • Dichlorobenzene is initially introduced in 40 ml of THF, and 2 ml of TMB are added. The remaining TMB is diluted with 10 ml of THF and added dropwise simultaneously with the LDA solution. The reaction temperature was maintained at 15°-25° C.
  • a solution of 4-ethoxy-2,3-difluorophenylboronic anhydride (3.7 g) in ethanol is added to a solution of 3.8 g of p-pentylbromobenzene and 0.16 g of tetrakis(triphenylphosphino)palladium (0) in a solvent mixture of benzene (20 ml) and 2M-Na 2 CO 3 (20 ml) at 20° C.
  • the mixture is heated at 95° C. for 30 hours. After cooling, the mixture is stirred at room temperature with 30% H 2 O 2 (2 ml) for 1 hour.
  • Customary workup and recrystallization give the pure product.
  • the 4-ethoxy-2,3-difluoro-4'-pentylbiphenyl can be used as an intermediate in the preparation of liquid crystal compounds as discussed in WO 89/08637, the disclosure of which is hereby incorporated by reference.

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5436361A (en) * 1994-04-22 1995-07-25 Clemson University Process for synthesizing enediynes
US20040230055A1 (en) * 2003-04-07 2004-11-18 Woltermann Christopher J. Using alkylmetal reagents for directed metalation of azaaromatics
KR100636466B1 (ko) 1998-12-19 2006-10-18 메르크 파텐트 게엠베하 오르토-치환된 아릴금속 화합물을 제조하고 이 화합물을 친전자성 시약과 반응시키는 방법
JP2010001300A (ja) * 2006-01-13 2010-01-07 Dow Agrosciences Llc ６−（多置換アリール）−４−アミノピコリネートおよび除草剤としてのそれらの使用
JP4941290B2 (ja) * 2005-03-03 2012-05-30 Ｊｎｃ株式会社 クロロフルオロベンゼン系液晶性化合物、液晶組成物および液晶表示素子
US10093781B2 (en) 2013-10-30 2018-10-09 Dow Global Technologies Llc Foamed styrenic polymers containing a brominated styrene-butadiene copolymer and having enhanced cell size homogeneity

Families Citing this family (2)

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Publication number Priority date Publication date Assignee Title
DE19858856A1 (de) * 1998-12-19 2000-06-21 Merck Patent Gmbh Verfahren zur Herstellung von Arylmetallverbindungen und deren Umsetzung mit Elektrophilen
JP5544695B2 (ja) * 2007-11-20 2014-07-09 Ｊｎｃ株式会社 光学的に等方性の液晶媒体及び光素子

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US5087764A (en) * 1988-03-10 1992-02-11 Merck Patent Gesellschaft mit beschrankter Hafung Process for the preparation of 2,3-difluorobenzenes

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US5087764A (en) * 1988-03-10 1992-02-11 Merck Patent Gesellschaft mit beschrankter Hafung Process for the preparation of 2,3-difluorobenzenes
EP0440082A2 (de) * 1990-02-01 1991-08-07 MERCK PATENT GmbH Verfahren zur Umsetzung von fluorierten Aromaten mit Elektrophilen

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5436361A (en) * 1994-04-22 1995-07-25 Clemson University Process for synthesizing enediynes
KR100636466B1 (ko) 1998-12-19 2006-10-18 메르크 파텐트 게엠베하 오르토-치환된 아릴금속 화합물을 제조하고 이 화합물을 친전자성 시약과 반응시키는 방법
US20040230055A1 (en) * 2003-04-07 2004-11-18 Woltermann Christopher J. Using alkylmetal reagents for directed metalation of azaaromatics
US7129360B2 (en) 2003-04-07 2006-10-31 Fmc Corporation Using alkylmetal reagents for directed metalation of azaaromatics
US7638635B2 (en) 2003-04-07 2009-12-29 Fmc Corporation Lithium Division Using alkylmetal reagents for directed metalation of azaaromatics
JP4941290B2 (ja) * 2005-03-03 2012-05-30 Ｊｎｃ株式会社 クロロフルオロベンゼン系液晶性化合物、液晶組成物および液晶表示素子
JP2010001300A (ja) * 2006-01-13 2010-01-07 Dow Agrosciences Llc ６−（多置換アリール）−４−アミノピコリネートおよび除草剤としてのそれらの使用
US10093781B2 (en) 2013-10-30 2018-10-09 Dow Global Technologies Llc Foamed styrenic polymers containing a brominated styrene-butadiene copolymer and having enhanced cell size homogeneity

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